5.27.8 PowerPC assembler

The PowerPC assembler and disassembler were contributed by Michal
Revucky.

This assembler does not follow the convention of ending mnemonic names
with a “,”, so some mnemonic names shadow regular Forth words (in
particular: and or xor fabs); so if you want to use the Forth
words, you have to make them visible first, e.g., with also
forth.

Registers are referred to by their number, e.g., 9 means the
integer register 9 or the FP register 9 (depending on the
instruction).

Because there is no way to distinguish registers from immediate values,
you have to explicitly use the immediate forms of instructions, i.e.,
addi,, not just add,.

The assembler and disassembler usually support the most general form
of an instruction, but usually not the shorter forms (especially for
branches).